docs: def get_story_prefixes(label_type, label_dir=LABEL_DIR):
      """ Gets the Na text prefixes. """
      prefixes = [prefix for prefix in os.listdir(os.path.join(label_dir, "TEXT"))
                  if prefix.endswith(".%s" % label_type)]
      prefixes = [os.path.splitext(os.path.join("TEXT", prefix))[0]
                  for prefix in prefixes]
      return prefixes